(maint) Fix output of ArithmeticExpression label (future parser)

If an ArithmeticExpression is involved in an error and a label
is output as part of the error message this led to an internal
error - undefined o_operator.

This fixes the problem (it should have been o.operator).
(#22442) Fix problem with missing issue ILLEGAL_NAME (future parser)

When a qualified name did not conform to the naming rule for
qualified names a reference was made to an undefined issue.

There was also a problem with the name validation rule as it was not
anchored at the beginning of the matched text. It thus allowed
variable names like `$Aaa` (which should also have been flagged as 
an error). Other naming validation patterns suffered from the same
problem.
(#22442) Update the name validation rule to not accept hyphens

The lexer does not allow them for the 3x standard of not allowing
hyphens in names. The validator should not use a more permissive rule.
(#22442) Add test that capitalized names are flagged as errors.

Capitalized variable names will not be allowed. The future parser
is more strict than 3x where this unfortunately was documented as
being ok.
Merge branch 'master' of https://github.com/puppetlabs/puppet